Tuesday, December 01, 2009

...we find that the Himalaya glaciers are difficult even for scientists to understand. Most suggestions of rapid melting are based on observations of a small handful of India's 10,000 or so Himalayan glaciers. A comprehensive report in November by senior glaciologist Vijay Kumar Raina, released by the Indian government, looked more broadly and found that many of these glaciers are stable or have even advanced, and that the rate of retreat for many others has slowed recently.

Jeffrey S. Kargel, a glaciologist at the University of Arizona, declared in the Nov. 13 issue of Science that these "extremely provocative" findings were "consistent with what I have learned independently," while in the same issue of the magazine Kenneth Hewitt, a glaciologist at Wilfrid Laurier University, agreed that "there is no evidence" to support the suggestion that the glaciers are disappearing quickly.

3 comments:

I've come to the conclusion that glaciers are a sub-optimal climate proxy. While they do melt (and thus shrink) when exposed to >0C temperatures, they are also eroded by wind. Also, they do not grow when the temperatures are <0C, as growth is fueled by precipitation and not the cold itself. This means that if it is cold enough, the air will be too dry for snow/rain to form, and the glaciers will only be affected by erosion. I believe this to be the case with the mt Kilimanjaro glacier, that has been shrinking at sub-zero temperatures since the turn of the last century at least.

So, depending on the location of the glacier, growth may be both a symptom of increasing and decreasing temperatures (more precipitation falling on it - either because of warmer, moister air coming in, or temperatures falling so that condensation occurs), while shrinkage may be a symptom of both too high or too low temperatures (melting, or non-condensing air) and possibly steady erosion.

Further, as glaciers are plastic, they tend to 'run' somewhat. Even with no mass-increase, this would be seen as growth. I believe they would be more 'runny' in warm weather than in cold weather, so glaciers would thus seem to 'grow' more in warmer than in colder weather as well. This would show these glaciers as an inverse climate-proxy.

As with tree-rings, which generally measure something else than temperature unless controlled very carefully in a lab setting, glaciers don't seem to be very good proxies at all.

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